Computational Method Of Motions And Wave Loads On Air Cushion Vehicle

The air cushion vehicle (ACV) was defined as a kind of ship that has the ability to make part of or all of the ship body out of the water surface so as to guarantee the sailing speed by the aid of the high-pressure air under the bottom. Due to its unmatchable advantages, the ACV was widely applied in the field of economy and military, and especially, the ACV-used-for-military developed quickly. However, so far the calculating method of ACV's loads induced in the wave is not so satisfactory and it is necessary to have a further study in the relevant area. In this paper, the air cushion stiffness (concerned with the carrying capability) and the analysis of motion response and loads response to the regular waves were studied.Main contents are as follows:1) The ACV's take-off properties were researched and the air cushion stiffness was calculated. Besides, the basic character of air cushion stiffness was studied.2) According to the linear theory of ACV's motion in the waves, with the method of transfer matrix, the solutions of heave and pitch in frequency domain were calculated, and then the sensitiveness to heave and pitch of several ship's typical parameters were analyzed.3) On the basis of the results of motion, the air-cushion dynamic pressure calculation formula was derived, and the midship-section loads induced in regular waves were calculated. A set of complete Fortran program was developed that linked the motion calculation with wave loads calculation. Meanwhile, the properties of the dynamic pressure and the loads under the different encounter frequency were discussed.4) A new method was originally created to calculate ACV's motion. With the enlightenment of Strip method, in this paper,3-D motion problems were simplified into 2-D motion problems. The motion of wave was described as the simple harmonic motion of the rigid bottom surface, and the motion of the strip was calculated to study the character of the air cushion as well as the strip motion and to provide reference to the whole ACV's motion calculation.